This invention is generally directed to imaging members comprised of a number of functional layers, one of which is a charge blocking layer, and more specifically, the present invention is directed to multi-layered imaging members with a hole blocking layer preferably situated in between a supporting substrate and a photoelectrically active layer, or photogenerator layer, and which blocking layer is comprised of a polymetallosiloxane, especially acid hydrolyzed sol-gel polymetallosiloxanes, wherein the metal is, for example, a transition metal or multivalent metals, examples of which are titanium, zirconium, aluminum, tin, germanium, lanthanum, zinc, boron, and the like. Examples of specific polymetallosiloxane materials that may be selected as the hole blocking layer are illustrated in "Polymetallosiloxane Coatings Derived from Two-step, Acid Base Catalyzed Sol Precursors for Corrosion Protection of Aluminum Substrates", by T. Sugama, J. R. Fair and A. P. Reed, Journal of Coatings Technology, Volume 65, No. 826, 1993, pages 17 to 36, the disclosure of which is totally incorporated herein by reference.
The primary function of the hole blocking layer is to prevent or minimize dark injection of positive charge, such as holes from the supporting substrate into the photogenerating layer, thereby eliminating or minimizing high dark decay and/or problems associated with localized areas of discharge, that is charge deficient spots. Moreover, even in the presence of the current flows occurring during normal photoreceptor operation, the blocking layers of the present invention provide uniform corrosion resistance and anodisation resistance, or minimization to substrates such as aluminum and nickel or other readily oxidized metals. Protection against damage from acidic species present in coating solvents is also provided in embodiments of the present invention.
The imaging members of the present invention in embodiments exhibit excellent electrical properties, cyclic and environmental stability, and substantially no adverse changes in performance over extended time periods. Processes of imaging, especially electrophotographic imaging and printing, including by digital means, are also encompassed by the present invention. More specifically, the invention layered photoconductive imaging members can be selected for a number of different known imaging and printing processes including, for example, both black and white and color electrophotographic imaging processes, especially xerographic imaging and printing processes wherein negatively charged images are rendered visible with toner compositions of an appropriate charge polarity. Moreover, the imaging members of this invention are useful in color xerographic applications where several color printings can be achieved in a single pass, and in processes were the color imaging is achieved by multiple passes of the imaging members past the exposure system, and in processes where a single imaging member is devoted to each primary color. The imaging members as indicated herein are in embodiments sensitive in the wavelength region of, for example, from about 400 to about 900 nanometers, and in particular, from about 600 to about 850 nanometers, thus diode lasers or LED image bars can be selected as the light sources.